Circuit breaker



Jul :30, 1940. M, PER ONS 2,29,611

CIRCUIT BREAKER Fi led Dec. 16, 1936 l fA/ 7 '0 E LA wen/c5 M Pi/PsomgPatented July so, 1940.

UNITED STATES CIRCUIT BREAKER Lawrence M. Persons, St. Louis, Mo.,assignor, by mesne assignments, to Automatic Control Corporation, St.Louis, Mo., a corporation of Delaware Application December 16, 1936,Serial No. 116,131

9 Claims.

The present invention relates generally to protective devices and moreparticularly to a thermally-actuatable circuit breaker which includes asnap make-and-break action and mechanism adapted to automatically resetthe contacts in make relation after a separation thereof.

An object of the present invention is to provide a thermally-actuatablecircuit breaker which is adapted to interrupt the electrical circuit ofan energy-translating device upon excessive current therethrough or upona dangerous internal overheating of the device.

Another object is to provide a thermally-actuatable circuit breakerwhich includes means for automatically resetting the device subsequentto a current interruption action thereof.

Another object is to provide a thermally-actuatable circuit breakerwhich includes a heating element adapted to actuate the circuit breakerby current passing therethrough.

Another object is to provide a thermally-actuatable circuit breakerwhich includes mechanism for closing and opening the contacts thereofwith a snap to prevent arcing.

Another object is to provide an electrical contact which is movablerelative to its support.

Another object is to provide a snap break action for a circuit breakerwhich includes means that effects movement of one contact relative toits support during said action.

Another object is to provide a thermally-actuatable circuit breakerwhich is adapted to efficiently and effectively protect anenergy-translating device, as a motor, under a variety of conditions.

Another object is to provide a thermally-actuatable circuit breakerwhich is compact in structure, cheap to manufacture and adapted in allrespects to fulfil all the purposes and advantages sought therefor.

Other objects and advantages will appear-from the following description,taken in conjunction with the accompanying drawing, in which:

Fig. 1 is a plan view of a thermally-actuatable circuit breakerconstructed in line with the present invention.

Fig. 2 is a side elevation of the circuit breaker shown in Fig. 1.

Fig. 3 is a section on the line 3'3 of Fig. 1, showing the contacts inmake relation.

Fig. 4 is a section on the line 3-3 of Fig. 2, showing the contacts inbreak relation.

Fig. 5 is a side elevation of the side of the circuit breaker oppositefrom that shown in Fig. 2. Fig. 6 is a section onthe line 65 of Fig. 2.Fig. '7 is a section on the line 1-1 of Fig. 3. Fig. 8 is a section onthe line 3-8 of Fig. 4.

Fig. 9 is a perspective of one type of bowed spring member employed inthe present device.

Fig. 10 is a perspective of one of the contacts and its support.

Referring to the drawing more particularly by reference numerals, I5indicates generally a circuit breaker constructed in line with oneembodiment of the present. invention, and includes a base I6 ofinsulative material. A U-shaped support generally indicated I1 is fixedto the base IS in inverted position, the bight l8 of the U being spacedfrom the said base l6 by substantially vertically disposed legs or wallsl9 and 20. Each of the legs includes a projection 2| which extendsthrough the base 6 (Fig. '7) and is peened over against a backing plate22 that is contiguous to the base l6 against the surface opposite tothat supporting the legs l9 and 20. A firm anchorage is thus establishedfor the support ll. Each of the legs [9 and further has a V-shaped notch23 and an opening 24 two sides of which define a V 25 oppositelydisposed to and slightly above the V-notch 23. The bight l8 includes amarginal recess 23 and a projection 29 which is offset as at 30 from theplane of the bight proper.

A substantially rectangular element or member generally designated 39has a central portion cut out, as is indicated at 32. The element 3! isadapted to be slipped over the support H and is supported thereby withone wall or pivot edge 33 resting in the V-notches 23 for pivotalmovement thereabout as a transverse axis. The element 3| includeslongitudinal flanges 36 for strengthening purposes and a transverseflange 35 across that end remote from the pivot edge 33. A fiat spring43 is fixed to the member M at 43' and supports at its free end acontact 42, which includes an enlarged head 42. The contact 42 extendsthrough a hole M in the member 3! so that the head 42' is located in theassemblage beneath the member 3i. The hole 44 is of a diameterintermediate the diameter of the neck of the contact 43 and the head 42'to prevent inadvertent withdrawal of the head 42' through the hole M.The spring 43 is biased towards the member- 39 so that the head 42 atall times has a force tending to push it downwardly (Fig. 4) from themember 3t. Such a movable contact prevents arcing. Of course, thecontact may be fixed directly to the member 3!, or otherwise springinfluenced relative thereto, if preferred.

A flexible member 36 of substantially rectangular configuration, whichincludes a longitudinal projection 37 at one end and two lateralprojections 38 at the other end, is disposed with the projection 3'!extending through a slot 4! in the flange 35 of the element 3| and theprojections 38 in the vs 25. Shoulders 39 adjacent the projection 31abut the inner face of the flange 35. The distance between the innerface of the flange 35 and the VS 25 is less than the distance betweenthe shoulders 33 and edges 30 of the projections 38 so that the member36 is maintained under bowed compression.

A J-shaped fabricated bimetallic member. generally designated 35includes a first section 65 which defines the shape of the member andserves as a base to which a second section l! of U- shape is welded.Obviously, a conventional construction may be used, if preferred. Thesection 56 terminates in a return bend 50 to provide a guide and supportfor a screw 5! that extends through threaded apertures 52 and 53 in thesection 66 proper and in the return bend 50, respectively. The member 35is connected to the projection 29 of the support H at 55 by welding,bradding, or the like. The member 55 and the support H are disposedthrough their connection 55 so that the long side of the J extends backover the support H to locate the screw 5i with its joint 53 above themember 3i just outwardly of the pivot line 33, whereby the screw 5! isadapted to pivot the member 3| about its pivotal support in a manner tobe described.

A U-shaped member generally designated 5i (Fig. 10) includes legs 58 and5S and a bight 63, which is bent at substantially right angles to thelegs 58 and 59 at 6| and 32. The leg 58 includes apertures 63 and 64while the leg 59 carries a contact 65. The member 5'! is fixed to thebase l6 by means of brads 66 which extend through the apertures 53 and 63. The member 51 is disposed so that the contact 55 lies directlybeneath the contact 32 for cooperative make-and-break action therewith.The leg 59 is bent relative to the bight 6B and the leg 58 so that, whenthe member 57 is in place on the base, the contact B5 is spaced from thesaid base It and is adapted to yield through its inherent resiliencywhen the contact 42 comes into make relation therewith. The contact 65may be mounted in fixed relation to the base It, if preferred. Where thecontact 42 is of the double movement type disclosed, the contact 65 isoften fixed to the base it.

A heater element 70 of a generally sinuous outline is disposed adjacentthe section 45 of the bimetallic member 35, and is connected at one endto a terminal ll fixed to said member 35 and at the other end to aterminal 12, which is supported by the base 55. A lead i3 is connectedto the terminal 72. A lead 74 is connected to one of the brads 56 and alead 15 is connected to the backing plate 22. The circuit breaker is, ofcourse, constructed of well known materials suitable for the variouselements.

Operation The thermally-actuatable circuit breaker just described isadapted to be used with energytranslating devices generally forprotective purposes, but it is particularly useful in conjunction with amotor. In practice, the circuit breaker is disposed within a casing of amotor in a position to receive substantially the full efiect of heatgiven forth by the motor windings. Hence, it is adapted to function tointerrupt the supply of current to the motor, either from ambient heatwithin the motor casing passing from the motor windings caused from acontinuous small overload, or the like, or from heat generated by theheater element effected by a short circuit or stoppage which would causeexcessive current to pass through the heater element as well as throughthe windings.

When the circuit breaker is installed within a motor casing and theleads are properly hooked aaoaen into the motor circuit in a mannerdesired, the elements of the circuit breaker will be disposed as isshown in Fig. 3, wherein the contacts 62 and 65 are in engagement, andthe screw 52is disposed with its point 53 spaced from the member 3|.

The bowed flexible member 36 is disposed with v When heat from whateversource reaches the bimetallic member 45 and is increased to an eiiectivevalue, stresses will be set up therein of a well-known nature, and thescrew 5i will be moved downwardly towards the member 3|. In itscontinued downward movement, due to a continued increase in temperature,the point 54 of the screw 5! will engage the member 3i and pivot itabout the pivot line 33 against the action of the flexible member 35.During the small initial movement of the member 3! while the forcetransmitted through the screw point is building up sufiiciently toovercome the effect of the spring 35 and the inertia of the elements,the contact 65 will follow the contact 42, maintaining an engagementtherewith due to the resiliency of its supporting member 57. The leverarm between the point 5 3 and the pivot line 33 is only a small fractionof the lever arm between the pivot line 33 and the abutments 39, and thevertical travel of the point 53 is a proportionately small fraction ofthe vertical travel of the abutment 39. The contact 62 is moved awayfrom the contact 35 with a snap action once the inertia of the elementsis overcome.

The movement of the members 3| a predetermined distance upwardly beforethe contact head 42' is withdrawn upwardly cooperates with the upwardspring of the contact 65 to assure a snap separation of the contacts,which prevents arcing and its resultant destruction of the contacts.Counterclockwise or upward movement (Fig. 3) of the member 3A is stoppedwhen the flange 35 comes into contact with the bimetallic member.Obviously, when the contacts are snapped apart, the current to themotor, or other device protected, is interrupted and damage from heat isprevented.

As the heat about the circuit breaker is dissipated, the bimetallicmember 45 moves back to its normal position, carrying with it the screw5!. The pressure on the member 3i is relieved, whereupon the flexiblemember 35 becomes effective to snap the contacts 12 and 65 into engagingrelation. 'The circuit breaker is then in operative conditionand isagain ready to protect the motor, or other device, upon which it may beinstalled.

It is clear that there has been provided a thermally-actuatable circuitbreaker which is adapted to fulfill all of the objects and advantagessought. It is to be understood that the above description and theaccompanying drawing have been given by way of example and illustrationand not by way of limitation, the invention being limited only by thefollowing claims.

What is claimed is:

1. A circuit breaker comprising a base, a support fixed to said base, amember pivotally mounted on said support having contact means, aresilient member having a fixed connection with the pivoted member andpivotal connection with the support, said contact carrying member andsaid resilient member cooperating to maintain both members in respectivepivotal relation on the support, second contact means disposed tocooperate with said first contact means, and cooperatively disposedthermally-actuatable means adapted to move said pivoted member to breakthe contacts.

2. A thermally-actuatable circuit breaker comprising a base, a U-shapedsupport fixed to said base having the bight thereof spaced therefrom bylegs in the form-oi walls, a V-notch in each wall, an aperture having aV as a part of the outline in each wall, a contact-carrying membersurrounding the support and pivoted thereto in the apices of theV-sha'ped notches, a -resilient member having a fixedfzfconnection withthe contactcarrying member and/a pivotal connection with the support inthe apices of the V-shaped portions of the apertures, second contactmeans connected to the base and disposed to cooperate with the firstcontact means, and a thermallyresponsive member fixed to the support anddisposed to move the contact-carrying member up- I to the support by aresilient member having a fixed connection with the pivoted member andpivotal connection with the support, second contact means disposed tocooperate with said first contact means, thermally-actuatable meansconnected to said support adapted to move said pivoted member to breakthe contacts, and a heater element disposed adjacent the bimetallicmember. Y

4. A circuit breaker comprising a base, a support including twosubstantially vertical walls fixed to said base, spaced opposed V-shapednotches in each of said walls, a contact-carrying member surroundingsaid support and pivotally engaging in one set of V-notches, a resilientmember having one end pivotally engaging said other set of notches andhaving the other end fixed to said contact-carrying member at the endremote from the pivotal connection of said contact-carrying member, asecond contact fixed to the base and disposed to cooperate, with saidfirst contact, and thermally-actuatable means fixed to said support andadapted to move said contact-carrying member to withdraw said firstcontact from said second contact, said break being effected with a snap.

5. A circuit breaker comprising a base, a support including twosubstantially vertical walls fixed to said base, spaced opposed V-shapednotches in each of said walls, a contact-carrying member surroundingsaid support and pivotally engaging in one set of V-notches, a resilientmember having one end pivotally engaging said other set of notches andhaving the other end fixed to said contact-carrying member at the endremote from the pivotal connection of said contact-carrying member, asecond contact fixed to the base and disposed to cooperate with saidfirst contact, thermally-actuatable means fixed to said support andadapted to move said contact-carrying member to withdraw said firstcontact from said second contact, said break being eflecte'd with asnap, and a heater element connected to said bimetallic element anddisposed adjacent thereto.

6. A thermally-actuatable circuit breaker comprising a base, a U-shapedsupport fixed to said base having the bight thereof spaced therefrom bylegs in the form of walls, a V-notch in each wall, an aperture having aV as a part of the outline in each wall, a contact-carrying membersurrounding the support and pivoted thereto in the apices of theV-shaped notches, a resilient member having a fixed connection with thecontact-carrying member and a pivotal connection with the support in theapices of the V-shaped portions of the apertures, said resilient memberbeing of greater length than the straight line distance between itsconnections, a line through the apices of the -V-notches being closer tothe base than a line through the apices of the V- portions of theapertures and said fixed connec-- tion between the contact-carryingmember and the resilient member being below a line drawn through theapices of thevs in one wall, second contact means connected to the baseand disposed to cooperate with the first contact means, and athermally-responsive member fixed to the support and disposed to movethe contact-carrying member upon increase in heat to break the contacts.

7. A circuit breaker comprising a base, a U- shaped support fixed tosaid base with the bight spaced therefrom, a member pivotally mounted onsaid support having contact means, a resilient member having a fixedconnection with the pivoted member and pivotal connection with thesupport maintaining said member in its pivotal relation to the support,second contact means disposed to cooperate with said firstcontact means,and operating means connected to said support adapted to move saidpivoted member to break the contacts.

8. A circuit breaker comprising a base, a support fixed to said base, amember having contact means pivotally mounted on said support, saidmember being maintained in its pivotal relation to the support by aresilient member having a fixed connection with'the pivoted member andpivotal connection with the support, second contact means disposed tocooperate with said first contact means, and means connected to saidsupport adapted to move said pivoted member to break the contacts.

9. A circuit breaker comprising a base, a U- shaped support fixed tosaid base having the bight thereof spaced therefrom by legs in the formof walls, a V-notch in each wall, an aperture having a V as a part ofthe outline in each wall, a contact-carrying member surrounding thesupport and pivoted thereto in the apices of the V-shaped notches, aresilient member having a fixed connection with the contact-carryingmember and a pivotal connection with the support in the apices of theV-shaped portions of the apertures, said resilient member being ofgreater length than the straight line distance between its connections,a line through the apices of the V-notches being closer to the base thana line through the apices of the V-portions of the apertures and saidfixed connection between the contact-carrying member and the resilientmember being below a line drawn through the apices of the Vs in onewall, second contact means connected to the base and disposed tocooperate with the first contact means, and a member fixed to thesupport and disposed to move the contactcarrying member to break thecontacts.

LAWRENCE M. PERSONS.

